<html><head><meta http-equiv="content-type" content="text/html; charset=utf-8"></head><body dir="auto"><div>There are those of us who need to maintain code that works on platforms older than GHC HEAD.</div><div><br></div><div>This would make it impossible to keep an API working across the change.</div><div><br>-Edward</div><div><br>On Oct 12, 2013, at 4:50 PM, Dan Burton <<a href="mailto:danburton.email@gmail.com">danburton.email@gmail.com</a>> wrote:<br><br></div><blockquote type="cite"><div><div dir="ltr">The back-compat can't replace code that uses the `Identity` data constructor, though. It will also make existing code bases ambiguous if they have defined their own `Id` data constructor. Pretty easy fixes, but nontrivial, so worth noting. Despite the pain involved, I think that Identity -> Id when moving this functor into base is a good choice.</div>
<div class="gmail_extra"><br clear="all"><div>-- Dan Burton</div>
<br><br><div class="gmail_quote">On Sat, Oct 12, 2013 at 12:40 PM, Dag Odenhall <span dir="ltr"><<a href="mailto:dag.odenhall@gmail.com" target="_blank">dag.odenhall@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div dir="ltr"><div><div class="im"><p style="margin:1.2em 0px!important">On Sat, Oct 12, 2013 at 7:32 PM, Edward Kmett <<a href="mailto:ekmett@gmail.com" target="_blank">ekmett@gmail.com</a>> wrote:</p>
<p style="margin:1.2em 0px!important"></p><div><p></p><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">On a related note Simon recently asked the core libraries committee if we should move Data.Functor.Identity into base.</blockquote>
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</div><p style="margin:1.2em 0px!important">How about calling that one <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px 3px 3px 3px;display:inline">Id</code> then (already in <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px 3px 3px 3px;display:inline">Data.Traversable</code> but not exported). This would be more consistent with <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px 3px 3px 3px;display:inline">Const</code> not being called <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px 3px 3px 3px;display:inline">Constant</code>. Maybe also put it in <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px 3px 3px 3px;display:inline">Control.Applicative</code> or move both somewhere better.</p>
<p style="margin:1.2em 0px!important">For back-compat, <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px 3px 3px 3px;display:inline">transformers</code> could continue to export those modules, with aliases like <code style="font-size:0.85em;font-family:Consolas,Inconsolata,Courier,monospace;margin:0px 0.15em;padding:0px 0.3em;white-space:pre-wrap;border:1px solid rgb(234,234,234);background-color:rgb(248,248,248);border-radius:3px 3px 3px 3px;display:inline">type Identity = Id</code>.</p>
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